1. Field of the Invention
The present invention relates to a suspension arm and cushion arm structure for a vehicle. The suspension arm structure includes a connected part between a drive shaft for transmitting power from an engine and a universal joint provided on the wheel side is covered with a boot. A knuckle is connected to a suspension arm swingably supported on a frame, a hub supported on a drive wheel is rotatably connected to the knuckle through a bearing, an axle is connected to the hub, and a drive wheel for transmitting power from an engine is connected to the axle through a universal joint. Left and right wheels are each swingably and independently suspended on the frame through the suspension arm, and a drive shaft for transmitting power from an engine to each of the wheels, the suspension arm being composed of upper and lower aims, a knuckle being supported by the upper and lower arms, the knuckle rotatably supporting the wheel, and a cushion being provided for absorbing shocks transmitted to the wheel.
2. Description of Background Art
As a vehicle in which left and right wheels are independently suspended, there has been known a vehicle wherein a knuckle is supported by upper and lower suspension arms swingably supported on a vehicle body frame, a wheel element of a wheel is connected to a hub rotatably supported by the knuckle, and each wheel is rotatingly driven by a drive shaft to which power of an engine is transmitted through a final speed reduction mechanism (refer to, for example, Japanese Patent Laid-Open No. 2001-328410).
In this vehicle, the connected part between the drive shaft and the wheel is composed of a universal joint, the connected part between the drive shaft and the universal joint is covered with a boot, and the boot protrudes outward beyond the depth (the width of a rim) of the wheel element of the wheel. Each of the suspension arms in this vehicle is formed in a roughly U shape by connecting one-side ends of front and rear pipes, and the other-side ends of the front and rear pipes are each swingably supported on the vehicle body frame, so that there is a clearance between the front and rear pipes.
When the vehicle body is viewed from the lower side, the boot is exposed through the clearance between the front and rear pipes of each of the suspension arms, so that it may be contemplated that, for all-terrain vehicle running mode, a protective member such as a guard is provided between the front and rear pipes of each of the suspension arms.
In conventional configurations, however, the provision of the protective member would complicate the structure of the suspension arm, and it is necessary, for example, to form the suspension arm in such a shape as to secure an attaching space for the protective member, or to provide the suspension arm with a bracket or the like for attaching the protective member. In addition, it is expected that increases in the number of component part and the weight will arise from the separate provision of the protective members.
In four-wheel vehicles such as ATV (All Terrain Vehicle), a knuckle is connected to a suspension arm swingably supported on a frame, a hub supported on a drive wheel is rotatably connected to the knuckle through a bearing, an axle is connected to the hub, and a drive wheel for transmitting power from an engine is connected to the axle through a universal joint (refer to, for example, Japanese Patent Laid-Open No. 2005-280619).
In such a vehicle, seal members are disposed respectively between the knuckle and the axle and between the knuckle and the hub, and penetration of mud, soil or the like into the bearing is prevented by these seal members.
In conventional configurations, in the case where a sealed bearing provided with a seal for preventing penetration of foreign matter is used as the above-mentioned bearing, the seal member between the knuckle and the axle and the seal member between the knuckle and the hub are not necessary; however, the removal of the seal members would lead to corresponding enlargement of the gap between the knuckle and the axle and the gap between the knuckle and the hub, in the vicinity of the knuckle, so that foreign matter such as mud and soil may penetrate during an ATV running mode. In addition, the gaps formed by omitting the above-mentioned seal members are comparatively large, it is difficult for the foreign matter having once entered to come out.
Furthermore, in conventional configurations, in vehicle having independently suspended left and right wheels, each suspension arm swingably supported on a vehicle body frame is typically composed of an upper arm and a lower arm, a knuckle is supported by the upper and lower arms, a wheel is connected to a hub rotatably supported by the knuckle, and shocks transmitted to the wheel are absorbed by a cushion.
Vehicles of this kind include those in which a cross member is provided at an intermediate part of the lower arm, and the lower end of the cushion is supported on the cross member (refer to, for example, Japanese Patent Laid-Open No. 2005-280619), and those in which the tip of the upper arm is bifurcated to form a bifurcated knuckle support part for supporting a knuckle, and the lower end of the cushion is supported between the bifurcation element parts of the bifurcated knuckle support part (refer to, for example, Japanese Patent Laid-Open No. 2003-002028).
However, in the configuration described in Japanese Patent Laid-Open No. 2005-280619, the cushion support part as a separate component part is provided at an intermediate part of the lower arm, and the number of component parts is therefore increased. In addition, a comparatively large cross member is used for securing the rigidity of the lower arm, and an increase in weight is therefore expected.
On the other hand, in the configuration described in Japanese Patent Laid-Open No. 2003-002028, the lower end of the cushion is supported between the bifurcation element parts of the bifurcated knuckle support part, and not any separate cushion support part is provided, so that an increase in the number of component parts can be suppressed accordingly In this configuration, however, it is impossible to earn the cushion stroke length, and the bifurcation of the knuckle support part leads to a complicated structure.